Gain Scheduling Control of Nonlinear Shock Motion Based on Equilibrium Manifold Linearization Model

AbstractThe equilibrium manifold linearization model of nonlinear shock motion is of higher accuracy and lower complexity over other models such as the small perturbation model and the piecewise-linear model. This paper analyzes the physical significance of the equilibrium manifold linearization model, and the self-feedback mechanism of shock motion is revealed. This helps to describe the stability and dynamics of shock motion. Based on the model, the paper puts forwards a gain scheduling control method for nonlinear shock motion. Simulation has shown the validity of the control scheme

An Experimental Study of the Water Transfer Through Confined Compacted GMZ Bentonite

International audienceGMZ bentonite has been considered as a possible material for engineered barrier in the Chinese program of nuclear waste disposal at great depth. In the present work, the hydraulic conductivity of this bentonite was determined by simultaneous profile method. A specific infiltration cell equipped with five resistive relative humidity probes was designed for this purpose. The water retention properties were studied under both confined and unconfined conditions; the results shows that at high suctions (> 4 MPa) the water retention capacity is independent of the confining condition, and by contrast, at low suctions (< 4MPa) the confined condition resulted in significant low water retention. Furthermore, the microstructure was investigated at Mercury Intrusion Porosimetry (MIP) and Environmental Scanning Electron Microscope (ESEM) in different states: on oven-dried powder, bentonite slurry, as-compacted and wetted samples. It has been observed that the soil powder is constituted of aggregates of various sizes; this aggregates are destroyed by fully saturation at a water content equal to the liquid limit; compaction at the initial water content of 11-12% and a dry density of 1.7 – 1.75 Mg/m3 led to a microstructure characterized by an dense assembly of relatively well preserved aggregates; saturation of the compacted sample under constant volume condition defined a non-homogeneous microstructure with the presence of well preserved aggregates. This non-homogeneous microstructure would be due to the non uniform distribution of the generated swelling pressure within the soil sample upon wetting. The hydraulic conductivity determined has been found decreasing firstly and then increasing with suction decrease from the initial value of about 80 MPa to zero; the decrease can be attributed to the large pore clogging due to soft gel creation by exfoliation process, as observed at ESEM

Linear Stability of f(R,ϕ,X)f(R,\phi,X) Thick Branes: Tensor Perturbations

We explore thick branes in $f(R,\phi,X)$ gravity. We obtain the linear tensor perturbation equation of $f(R,\phi,X)$ branes and show that the branes are stable against the tensor perturbations under the condition of $\frac{\partial f(R,\phi,X)}{\partial R}>0$. In order to obtain thick brane solutions of the fourth-order field equations in this theory, we employ the reconstruction technique. We get exact solutions of the specific $f(R,\phi,X)$ thick brane generated by a non-canonical scalar field. It is shown that the zero mode of the graviton for the thick brane is localized under certain conditions. This implies that the four-dimensional Newtonian potential is recovered on the brane. The effects of the Kaluza-Klein modes of the graviton for the $f(R,\phi,X)$ thick brane are also discussed.Comment: 23 pages, 5 figure

Investigation on gas migration in saturated materials with low permeability

International audienceInvestigation of the hydro-mechanical effects on gas migration in saturated materials with low permeabilityis of great theoretical and practical significances in many engineering fields. The conventional two-phaseflow (visco-capillary flow) theory, which regards the capillary pressure as the only controlling factor in gasmigration processes, is commonly adopted to describe the gas flow in geo-materials. However, formaterialswith lowpermeability, the conventional two-phase flow theory cannot properly describe the gasmigration.In this work, hydro-mechanical coupled gas injection tests were conducted. The volumetric variation of theliquid for applying the confining pressure in the specimen cell and the gas flow rate were monitored. Testresults indicate that gas migration is influenced by the capillary pressure and the mechanical stress simultaneously.The two key parameters of the gas entry pressure Pentry and the gas induced-dilatancy pressurePdilatancy are introduced for description of gas migration with respect to the capillary pressure and the mechanicalstress effects, respectively. When the gas injection pressure is smaller than the Pentry and thePdilatancy, the balance between the gas injection pressure and the confining pressure will lead to an intermittentgas flow. Sudden increase of gas flow rate could be observed once the gas injection pressure approachesthe Pentry or the Pdilatancy. For higher gas injection pressures, the mechanical stress effects on gas migrationcould not be neglected. The sudden increase of gas flux under high gas injection pressures could be causedby the mechanical induced-dilatancy of channels, capillary pressure induced-continuous flow pathways, aswell as the failure of sealing-efficiency. The failure of sealing-efficiency is closely related to the differencebetween the gas injection pressure and the confining pressure rather than the properties of the materialtested. Monitoring the volume of liquid for applying confining pressure is helpful for detecting the failureof sealing efficiency and the mechanism of gas breakthrough

Simulation Analysis on Flow Field and Temperature Field in Mould of Special Thick Slab Caster

A three-dimensional model of the thick slab continuous casting mould of 400 × 2200 mm was established. The effects of immersion depth of nozzle and casting speed on the flow field and temperature field were investigated. The high temperature distribution in mould, the thickness of narrow face solidified shell, the impact position of stream and the free surface velocity were used as the main points of analysis. Simulation and practical water modelling both exhibited the same changing trends, namely, the flow velocity of the surface increases with the distance from nozzle. The scientific basis for optimizing the flow field and temperature field in the continuous casting of special thick slab mould was acquired through calculations

Thermal-mechanical behavior of compacted GMZ Bentonite

International audienceThe THM behavior of compacted GMZ bentonite has been investigated using a suction-temperature controlled isotropic cell. The results obtained were compared with the existing results on other reference bentonites (MX80, FEBEX, FoCa, and Kunigel-V1). It has been observed that the coefficient of thermal expansion of the compacted GMZ bentonite is 2 x 10-4°C-1, similar to the values of compacted MX80 and FEBEX bentonites. The heating tests of the GMZ bentonite also show that the suction is an important parameter that governs the thermal volumetric behavior of unsaturated soils. Unlike temperature, suction has a significant effect on the compressibility parameters. Examination of the mineralogy of various bentonites showed that a good correlation can be generally established between the montmorillonite content and the cations exchange capacity (CEC) or the specific surface area (S). Nevertheless, both the basic geotechnical properties and the swelling potential seem to depend not only on the montmorillonite content but also on other factors such as the nature of base exchangeable cations. The quartz content of the GMZ bentonite is relatively high (11.7%). This could explain its relatively large values of thermal conductivity

Temperature Effects on the Unsaturated Permeability of the Densely Compacted GMZ01 Bentonite under Confined Conditions

International audienceIn this study, temperature controlled soil-water retention tests and unsaturated hydraulic conductivity tests for densely compacted Gaomiaozi bentonite - GMZ01 (dry density of 1.70 Mg/m3) were performed under confined conditions. Relevant soil-water retention curves (SWRCs) and unsaturated hydraulic conductivities of GMZ01 at temperatures of 40°C and 60°C were obtained. Based on these results as well as the previously obtained results at 20°C, the influence of temperature on water-retention properties and unsaturated hydraulic conductivity of the densely compacted Gaomiaozi bentonite were investigated. It was observed that: (i) water retention capacity decreases as temperature increases, and the influence of temperature depends on suction; (ii) for all the temperatures tested, the unsaturated hydraulic conductivity decreases slightly in the initial stage of hydration; the value of the hydraulic conductivity becomes constant as hydration progresses and finally, the permeability increases rapidly with suction decreases as saturation is approached; (iii) under confined conditions, the hydraulic conductivity increases as temperature increases, at a decreasing rate with temperature rise. It was also observed that the influence of temperature on the hydraulic conductivity is quite suction-dependent. At high suctions (s > 60 MPa), the temperature effect is mainly due to its influence on water viscosity; by contrast, in the range of low suctions (s < 60 MPa), the temperature effect is related to both the water viscosity and the macro-pores closing phenomenon that is supposed to be temperature dependent

PVO: Panoptic Visual Odometry

We present PVO, a novel panoptic visual odometry framework to achieve more comprehensive modeling of the scene motion, geometry, and panoptic segmentation information. Our PVO models visual odometry (VO) and video panoptic segmentation (VPS) in a unified view, which makes the two tasks mutually beneficial. Specifically, we introduce a panoptic update module into the VO Module with the guidance of image panoptic segmentation. This Panoptic-Enhanced VO Module can alleviate the impact of dynamic objects in the camera pose estimation with a panoptic-aware dynamic mask. On the other hand, the VO-Enhanced VPS Module also improves the segmentation accuracy by fusing the panoptic segmentation result of the current frame on the fly to the adjacent frames, using geometric information such as camera pose, depth, and optical flow obtained from the VO Module. These two modules contribute to each other through recurrent iterative optimization. Extensive experiments demonstrate that PVO outperforms state-of-the-art methods in both visual odometry and video panoptic segmentation tasks.Comment: CVPR2023 Project page: https://zju3dv.github.io/pvo/ code: https://github.com/zju3dv/PV

Optical effects of spin currents in semiconductors

A spin current has novel linear and second-order nonlinear optical effects due to its symmetry properties. With the symmetry analysis and the eight-band microscopic calculation we have systematically investigated the interaction between a spin current and a polarized light beam (or the "photon spin current") in direct-gap semiconductors. This interaction is rooted in the intrinsic spin-orbit coupling in valence bands and does not rely on the Rashba or Dresselhaus effect. The light-spin current interaction results in an optical birefringence effect of the spin current. The symmetry analysis indicates that in a semiconductor with inversion symmetry, the linear birefringence effect vanishes and only the circular birefringence effect exists. The circular birefringence effect is similar to the Faraday rotation in magneto-optics but involves no net magnetization nor breaking the time-reversal symmetry. Moreover, a spin current can induce the second-order nonlinear optical processes due to the inversion-symmetry breaking. These findings form a basis of measuring a pure spin current where and when it flows with the standard optical spectroscopy, which may provide a toolbox to explore a wealth of physics connecting the spintronics and photonics.Comment: 16 pages, 7 fig